36 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



character, and some specimens of G. gracilis from Lake Superior actually have only one or two 

 more segments thau the subtenauean species. In the antennae there are no constant differences. 

 There are some very slight differences in the first and second pairs of legs, especially in the 

 females, but not greater than usually exist in the individuals of a single species in allied genera, 

 and any large series of specimens would undoubtedly show all the intermediate forms. In the 

 third to the seventh pairs of legs there is a constant difference in all^fche specimens examined, the 

 spines being more numerous, longer, and more slender in C. gracilis. The spines upon the first 

 and second pairs of caudal stylets are a little shorter and more obtuse in G. pacTcardii than they 

 usually are in G. gracilis; otherwise there is no difference in the caudal stylets and telson. 



These differences are all such as very naturally lead to the supposition that this subterranean 

 form has been derived from the G. gracilis at no very remote period, although this supposition 

 may well be held in reserve until we have a more complete series of the subterranean species for 

 comparison. C. gracilis occurs as far south as Grand Eapids, Michigan, whence we have received 

 specimens from Mr. N. Coleman, and it very likely occurs in the same region as G. paclcardii. 



The figures are all from Professor Packard's original specimens, collected from wells in 

 Orleans, Indiana, by Dr. Moses N. Elrod. Only one of these has the body entire ; this is a female, 

 5.5 mm long, from which Figs. 5 to 8 were made. A larger specimen, a female about 7.5 mm long, 

 unfortunately wanting most of the antennulae and antennae, collected from a well at New Albany, 

 Indiana, by Dr. John Sloan, was sent to Dr. Packard for examination. 



Figs. 5 to 11. — Crangonyx paclcardii, details all enlarged 48 diameters ; 5 to 8, female, 5.5 min 

 long; 9 to 11, female, about 7.5 mm long: 5, lateral view of head; 6, terminal portion of one of the 

 first pair of legs, outside; 7, same of second pair; 8, terminal portion of abdomen, lateral view; 9, 

 one of the first pair of legs, outside; 10, one of second pair of legs, outside; 11, antennula and 

 antenna, side view. [All the figures, 1 to 11, drawn by Prof. S. I. Smith.] 



Crangonyx antennatus Pack. 



Crangonyx antennatus Pack., Amer. Naturalist, xv, 880, 1881. 



The second crustacean discovered swimming about in the subterranean stream of Nickajack 

 Cave was a species of Amphipod belonging to the genus Crangonyx, and has been described as 



Fig. 5. — Crangonyx antennatus Packard, a, end of abdomen and appendages ; 6, head, with base of upper aDd entire lower antennae and 



eyes ; o, nianus of second pair of feet ; all enlarged. 



Crangonyx antennatus Packard. * It is a large purplish species, with very long antennae, and dis- 

 tinct, well-developed black eyes. 



* It is a large and purplish species; the first antennae very long; the flagellum with 20 to 24 joints ; the entire 

 antennae being over oue-half and nearly two-thirds as long as the body ; the last joint of the peduncle being slightly 

 more than half as long as the penultimate joint. Compared with C. gracilis Smith, from Lake Superior, it differs in 

 the form of the eyes, the longer and stouter first antennae, the flagellum having a greater number of joints, and in the 

 different proportions of the jeints of the peduncle; the second joint of the latter being much longer than in C. gracilis, 

 while the first joint of the scape is much longer, and the second and third joints one-third longer in proportion than 

 in C. gracilis. The fourth pair of epimera are unusually large and nearly square. The telson, together with the caudal 

 stylets, is much as in C. gracilis, but the rami are slightly stouter and more polished, and the spinules a little stouter. 

 It probably is a little larger species than C. gracilis, the specimens being 6 to7 mm in length; the eyes are not so 

 distinct, and are only one-fourth as large as in C. gracilis. It is very different from C. vitreus (Cope), of Mammoth 

 Care, and from C. jpackardii Smith, differing in its distinct eyes, and larger, more numerously-jointed antennae. 



